There's a good amount of subjectivity regarding baseball prospects. With the evaluation of talent being in the eye of the beholder, finding consensus is often difficult. Even Jim Callis and Jonathan Mayo of MLBPipeline.com don't always see eye to eye. They discuss their viewpoints regularly in a feature called Pipeline Perspectives. Submit a topic for them to debate.

For now, the Cardinals and Cubs take up opposite ends on the spectrum of relevancy.

Three years removed from its most recent World Series championship and a year away from its last National League pennant, St. Louis currently holds the second NL Wild Card spot and stands just a game back in the NL Central. Chicago hasn't played in a Fall Classic since 1945 and won't this year, as it has the second-worst record in the NL and the fourth-worst in the Major Leagues.

The longtime rivals do share at least one thing in common, however. Both the Cardinals and Cubs have added one of the game's elite young hitting prospects to their lineups. St. Louis promoted outfielder Oscar Taveras to the big leagues for the first time at the end of May and for good a month later, while infielder Javier Baez will join Chicago's roster today.

Regarded the best pure hitting prospect in baseball, the 22-year-old Taveras has barreled balls since turning pro for $145,000 out of the Dominican Republic in 2008. He batted .320/.376/.516 in the Minors, winning batting titles in the low Class A Midwest League in 2011 and the Double-A Texas League in 2012. St. Louis sent the slumping Allen Craig to the Red Sox in a July 31 trade for John Lackey to clear space for Taveras to play regularly.

The 21-year-old Baez, a native of Puerto Rico, has destroyed baseballs since the Cubs signed him for $2.625 million as the ninth overall pick in the loaded 2011 Draft. His electric bat speed is reminiscent of Gary Sheffield's and has produced 76 homers in 319 Minor League games. He led the Minors with 75 extra-base hits and 111 RBIs in 2013 and recovered from a slow start in Triple-A this year to bash 12 homers in his last 32 games, not to mention one off the Nationals' Lucas Giolito in the Futures Game.

The question for today's Pipeline Perspectives is which phenom will be the more productive big leaguer for the remainder of the season? Jonathan Mayo believes more in Baez, but Taveras is the better bet for a variety of reasons.

The most obvious is Taveras' ability to repeatedly make hard contact, the product of his quick left-handed swing and mature approach at the plate. He struck out just 243 times in 1,860 plate appearances in the Minors. Though he hasn't been tearing up Major League pitching, batting .220/.259/.321, he has fanned just 15 times in 116 trips to the plate.

Baez is supremely talented but also wildly undisciplined. He'll swing at just about anything, and while he can crush balls out of the strike zone, he also can look foolish. He has 350 strikeouts and just 88 walks in 1,350 pro plate appearances, and he has the second-worst swing-and-miss percentage (37 percent) and third-worst strikeout percentage (30 percent) in the Triple-A Pacific Coast League this year (according to minorleaguecentral.com).

It took Baez nearly two months to get his batting average above the Mendoza Line in the PCL, and while he did make some adjustments, he'll likely face a steep learning curve against big league pitchers. Even patient hitters usually need time to adapt to the Majors. Taveras has, and he has the advantage of already having two months under his belt at the game's highest level.

Though he has yet to have his first big league at-bat, Baez will become Chicago's second-most dangerous hitter (behind Anthony Rizzo) as soon as he enters the lineup. Don't be surprised if teams pitch around Baez more than they do most rookies -- and if he obliges them by chasing pitches out of the strike zone.

Baez also has the handicap of breaking into the Majors at the relatively unfamiliar position of second base. He never had played anywhere but shortstop in a pro game before the All-Star break, spending 16 of his last 20 PCL contests at second base. It's difficult to learn a new position on the fly at the big league level, which could take a toll on his offensive production.

Because he's undisciplined, surrounded by a lesser supporting cast and still figuring out the nuances of second base, Baez likely will exhibit severe growing pains in August and September. Taveras is better suited to producing during the stretch drive, plus he's in a more comfortable role and already is starting to learn the adjustments he needs to make. Both Baez and Taveras are future All-Stars, but Taveras will more closely resemble one in the final two months.

Jim Callis is a reporter for MLB.com and writes a blog, Callis' Corner. Follow @jimcallisMLB on Twitter. This story was not subject to the approval of Major League Baseball or its clubs.